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Variable-energy (0–30keV) positron beam studies have been carried out on 200 keV Se-implanted and 70 keV Si-implanted GaAs specimens before and after annealing for electrical activation. From the measurements of Doppler broadened profiles as a function of incident positron energy, it was found that vacancy clusters with high concentration were introduced in the annealed specimen after Se implantation. From the parallel measurement of electrical characteristics, a higher activation efficiency was found for the higher concentration of vacancy clusters. That fact implies that electrons supplied by the activation of Se also convert the charge state of As vacancies from positive to negative. In contrast, no vacancy clusters were introduced in the Si-implanted GaAs. On the other hand, oxygen clustering was found in annealed specimen after O implantation.

Diamond superlattices were fabricated by producing multilayer structures of isotopically pure carbon-12 (12C) and carbon-13 (13C), which confine electrons by a difference in band-gap energy. Secondary ion mass spectrometry (SIMS) measurements were employed to characterize the isotopic composition of the diamond superlattices. Layers between 2 nm and 350 nm in thickness can be designed and fabricated using a microwave plasma-assisted chemical vapor deposition technique.

Seasonal variations in cause- and age-specific suicide rates in males and females were analysed in Osaka, Japan, for the years 1974–83, using profile analysis. Significant cause differences were found in males: (1) the rate for poisoning by domestic, car-exhaust or other gases was high in winter and spring and low in summer and autumn; (2) the rate for hanging, strangulation and suffocation was low in winter; (3) the rate for a variety of violent methods (chemicals, firearms, drowning, etc.) was high in summer. Similarly, there were sex differences in the variation for causes (2) and (3) and for ages 40–54. No significant age difference was found in either sex. Seasonal differences in the ease of suicidal methods and sex- and season-specific psychosocial factors were thought to be the major determinant of the seasonal variation.

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